Silicon carbide semiconductor device and method of manufacturing a silicon carbide semiconductor device

1. A silicon carbide semiconductor device comprising: a semiconductor substrate of a first conductivity type; a first semiconductor layer of the first conductivity type provided on the semiconductor substrate, the first semiconductor layer having an impurity concentration that is lower than an impurity concentration of the semiconductor substrate; a second semiconductor layer of a second conductivity type provided on a first side of the first semiconductor layer, opposite a second side of the first semiconductor layer facing toward the semiconductor substrate; a first semiconductor region of the first conductivity type selectively provided in a surface layer of the second semiconductor layer, the first semiconductor region having an impurity concentration that is higher than the impurity concentration of the semiconductor substrate, the surface layer being on a first side of the second semiconductor layer, opposite a second side of the second semiconductor layer facing toward the first semiconductor layer; a gate electrode provided opposing at least a part of a surface of the second semiconductor layer between the first semiconductor region and the first semiconductor layer, across a gate insulating film; and a first electrode provided on the surface of the second semiconductor layer and the first semiconductor region, wherein protons are implanted in a first region of the semiconductor substrate, the first region spanning at least 2 μm from a surface of the semiconductor substrate facing toward the first semiconductor layer and in a second region of the first semiconductor layer, the second region spanning at least 3 μm from a surface of the first semiconductor layer on the second side of the first semiconductor layer facing toward the semiconductor substrate, the protons are implanted in the first region with a concentration in a range from 1×10 13 /cm 3 to 1×10 15 /cm 3 , the protons are implanted in the second region with a concentration in a range from 1×10 13 /cm 3 to 1×10 15 /cm 3 , and the first region corresponds to a portion of the semiconductor substrate, and protons are not implanted in another portion of the semiconductor substrate.

2. The silicon carbide semiconductor device according to claim 1 , wherein the protons are implanted in a region of the first semiconductor layer other than the second region at a concentration of less than 1×10 13 /cm 3 .

3. The silicon carbide semiconductor device according to claim 1 , wherein the protons are implanted in the gate insulating film.

4. The silicon carbide semiconductor device according to claim 1 , wherein helium is implanted in place of the protons.

5. The silicon carbide semiconductor device according to claim 1 , wherein the protons are not implanted in the gate insulating film.

6. A method of manufacturing a silicon carbide semiconductor device, the method comprising: forming a first semiconductor layer of a first conductivity type on a semiconductor substrate of the first conductivity type, the first semiconductor layer having an impurity concentration lower than an impurity concentration of the semiconductor substrate; forming a second semiconductor layer of a second conductivity type on a first side of the first semiconductor layer, opposite a second side of the first semiconductor layer facing toward the semiconductor substrate; selectively forming a first semiconductor region of the first conductivity type in a surface layer of the second semiconductor layer on a first side of the second semiconductor layer, opposite a second side of the second semiconductor layer facing toward the first semiconductor layer, the first semiconductor region having an impurity concentration higher than an impurity concentration of the semiconductor substrate; forming a gate electrode opposing at least a part of a surface of the second semiconductor layer between the first semiconductor region and the first semiconductor layer, across a gate insulating film; irradiating protons in a first region of the semiconductor substrate, the first region spanning at least 2 μm from a surface of the semiconductor substrate facing toward the first semiconductor layer, the protons irradiated and implanted in the first region having a concentration in a range from 1×10 13 /cm 3 to 1×10 15 /cm 3 , irradiating protons in a second region of the first semiconductor layer, the second region spanning at least 3 μm from a surface of the first semiconductor layer on the second side of the first semiconductor layer facing toward the semiconductor substrate, the protons irradiated and implanted in the second region having a concentration of-the protons being in a range from 1×10 13 /cm 3 to 1×10 15 /cm 3 ; and forming a first electrode on surfaces of the first semiconductor region and the second semiconductor layer, wherein the first region corresponds to a portion of the semiconductor substrate, and protons are not implanted in another portion of the semiconductor substrate.

7. The method according to claim 6 , wherein irradiating the protons includes irradiating the protons from a side of the semiconductor substrate facing toward the first electrode, and the method further includes performing heat treatment at a temperature of 420 degrees C. or less after forming the first electrode.

8. The method according to claim 6 , wherein irradiating the protons includes irradiating the protons from a first side of the semiconductor substrate, opposite a second side of the semiconductor substrate facing toward the first electrode, and the method further includes performing heat treatment at a temperature of 420 degrees C. or less after forming the first electrode.